1. Field of the Invention
The present invention is directed generally to a process for producing an electrophotographic photoreceptor and, more particularly, is directed to a process for producing an electrophotographic photoreceptor comprising a conductive substrate having provided thereon a photoconductive layer comprising amorphous silicon and a surface protection layer comprising amorphous silicon carbide or amorphous carbon.
2. Description of Related Art
A recent development in the art of electro-photographic photoreceptors is a photoreceptor having an amorphous silicon photosensitive layer, and a variety of various amorphous silicon-based electro-photographic photoreceptors have already been proposed. Photoreceptors having an amorphous silicon photosensitive layer are produced by forming an amorphous silicon film on a conductive substrate by, for example, decomposition of silane (SiH.sub.4) by glow discharge. The amorphous silicon film contains hydrogen atoms to thereby exhibit photoconductivity. Notwithstanding the fact that amorphous silicon photoreceptors have a high degree of sensitivity to light having wave-lengths of from about 400 to 700 nm, a high level of heat resistance as well as excellent mechanical strength, an additional layer comprising, for example, SiN and SiO, has been proposed as a surface protection layer for the amorphous silicon film. It has been pointed out, however, that such surface protection layers cause blurring of images when subjected to long-term use under high temperature and high humidity conditions. In order to solve this problem, certain electrophotographic photoreceptors have been proposed which have surface layers comprising amorphous silicon carbide, amorphous carbon, or carbon of diamond structure as disclosed in unexamined, published Japanese patent application Nos. JP-A-57-115551, JP-A-57-115556, JP-A-58-88753, JP-A-57-114146, JP-A-60-61761, and JP-A-60-249155.
Amorphous silicon carbide surface layers are generally formed on the photoreceptor surface by glow discharge decomposition of a mixed gas comprising a hydrocarbon gas and a silicon hydride gas, and amorphous carbon surface layers are generally formed on the photoreceptor surface by glow discharge decomposition of a hydrocarbon gas. The surface layers thus formed, however, exhibit a low hardness level as evidenced by low Vickers hardness values which range from about 300 to 400 (load=10 g). Accordingly, the surface of such photoreceptors tend to be susceptible to physical deformation and alteration during use as a result of frictional contact with the blade used for scraping residual toner and/or contact with a pawl used for releasing paper. Once the surface integrity of the photoreceptor is broken, image quality becomes reduced and defective electrophotographic copies having streaks and similar faults result.